1. Field of the Invention
This invention relates to a process of fabrication of infrared photodiodes and the photodiodes.
2. Brief Description of the Prior Art
There is presently a problem in meeting required specification performance with sufficient margin in staring focal plane arrays (FPAs) when operating at temperatures higher than 77.degree. Kelvin and up to about 110.degree. Kelvin. The present approach of ion implanting long wave infrared (LWIR) material has the advantage of ease of fabrication in a manufacturing environment, however this approach has an inherent limitation of high dark currents at the aforementioned elevated operating temperatures. These dark currents are currents created in the vicinity of the pn junctions independent of any infrared light impinging upon the diode. It is the infrared light which impinges upon the diode that is to be measured. Inherently, electron-hole pairs are generated spontaneously around the pn junction by thermal and field motivated mechanisms. It is these dark currents that impede the ability of the diode to detect small signals. It is also desirable to operate with a single cooling gas at temperatures higher than the present liquid nitrogen which is 77.degree. K. Generally, the higher the possible operating temperature of the system, the lower the cost of operation. Accordingly, operation at the temperature of liquid argon which is 88.degree. to 90.degree. Kelvin or at even higher temperatures is desirable. At present, the signal to noise ratio of the above described system is generally not tolerable with operation at temperatures higher than that of liquid nitrogen.